added description of the project

.project

@@ -17,7 +17,12 @@
 		<link>
 			<name>ise_logs/ISExst.log</name>
 			<type>1</type>
-			<location>/home/andrey/git/x353/ise_logs/ISExst-20150726001950045.log</location>
+			<location>/home/andrey/git/x353/ise_logs/ISExst-20150726141146079.log</location>
+		</link>
+		<link>
+			<name>ise_state/x353-synth.tgz</name>
+			<type>1</type>
+			<location>/home/andrey/git/x353/ise_state/x353-synth-20150726135708468.tgz</location>
 		</link>
 	</linkedResources>
 </projectDescription>

README.md

+x393
+=====
+
+FPGA code for Elphel NC353 camera, updated to work with [VDT plugin](https://github.com/Elphel/vdt-plugin)
+
+This repository is created as a reference for simulation of image acquisition, processing and compression
+in the new NC393 camera that includes functionality of the previous one, so the same input image (on one of
+the 4 channels) should generate the same intermediate and final compressed files on both cameras.
+
+We will also try to make it possible to generate functional bitstream files compatible with the existing
+NC353 camera (so others will be able to modify their camera code with the current version of Xilinx tools),
+but we are not there yet - ***this project is valid for simulation only!***
+
+Here is what makes it difficult:
+
+1. Xilinx abandoned support of the older devices in the current software called "Vivado".
+2. Last verion of the ISE (it is ISE 14.7) can not use the older code "as is"
+3. We were able to modify the Verilog code to be parsed by the current XST, but it does not
+recognize some statements in the *.xcf constraints file (I had to rename original *.ucf to *.xcf).
+4. Attempt to try old parser (Suggested by XST itself as the new parser is not the default for
+the Spartan 3e): 
+```
+WARNING:Xst:3152 - You have chosen to run a version of XST which is not the default solution
+   for the specified device family. You are free to use it in order to take
+   advantage of its enhanced HDL parsing/elaboration capabilities. However,
+   please be aware that you may be impacted by  language support differences.
+   This version may also result in circuit performance and device utilization
+   differences for your particular design. You can always revert back to the
+   default XST solution by setting the "use_new_parser" option to value "no" 
+   on the XST command line or in the XST process properties panel.
+```
+also failed. After I added recommended options:
+```
+run  -use_new_parser no -ifn  x353.prj  -ofn x353.ngc  -top x353  -p xc3s1200eft256  -uc x353.xcf  -opt_mode speed  -opt_level 1 
+```
+and ISE noticed that:
+```WARNING:Xst:1583 - You are using an internal switch '-use_new_parser'.
+```
+It still repeated the same  WARNING:Xst:3152 (see above) disregarding its own suggestion.
+
+So we will need to find a way how to replace lines in the *xst file that cause errors in XST:
+```
+204 TIMEGRP "CPU_ADDR" =   pads("A<*>");
+205 TIMEGRP "CPU_ADDRCE" = "CPU_ADDR"  pads("CE*");
+206 TIMEGRP "CPU_DATA" =   pads("D<*>");
+207 TIMEGRP "WE" =         pads("WE");
+208 TIMEGRP "OE" =         pads("OE");
+209 TIMEGRP "DACK_PAD"=    pads("DACK*");
+209 TIMEGRP "DREQ_PAD"=    pads("DREQ*");
+210 TIMEGRP "ALLPADS"=     pads("*");
+```
+```
+ERROR:Xst:1888 - Processing TIMEGRP CPU_ADDR: User group 'pads("A<*>")' defined from other
+                 user group pattern not supported.
+```
+Even Google does not know what to do about this Xilinx XST feature: No results found for "ERROR:Xst:1888".
+
+So we'try to find other ways to re-formulate old timing constraints preserving the same meaning and try
+again to run tools.